/*
Copyright 2024 The Matrix.org Foundation C.I.C.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import { PhasedRolloutFeature } from "../../src/utils/PhasedRolloutFeature";

describe("Test PhasedRolloutFeature", () => {
    function randomUserId() {
        const characters = "abcdefghijklmnopqrstuvwxyz0123456789.=_-/+";
        let result = "";
        const charactersLength = characters.length;
        const idLength = Math.floor(Math.random() * 15) + 6; // Random number between 6 and 20
        for (let i = 0; i < idLength; i++) {
            result += characters.charAt(Math.floor(Math.random() * charactersLength));
        }
        return "@" + result + ":matrix.org";
    }

    function randomDeviceId() {
        const characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        let result = "";
        const charactersLength = characters.length;
        for (let i = 0; i < 10; i++) {
            result += characters.charAt(Math.floor(Math.random() * charactersLength));
        }
        return result;
    }

    it("should only accept valid percentage", () => {
        expect(() => new PhasedRolloutFeature("test", 0.8)).toThrow();
        expect(() => new PhasedRolloutFeature("test", -1)).toThrow();
        expect(() => new PhasedRolloutFeature("test", 123)).toThrow();
    });

    it("should enable for all if percentage is 100", () => {
        const phasedRolloutFeature = new PhasedRolloutFeature("test", 100);

        for (let i = 0; i < 1000; i++) {
            expect(phasedRolloutFeature.isFeatureEnabled(randomUserId())).toBeTruthy();
        }
    });

    it("should not enable for anyone if percentage is 0", () => {
        const phasedRolloutFeature = new PhasedRolloutFeature("test", 0);

        for (let i = 0; i < 1000; i++) {
            expect(phasedRolloutFeature.isFeatureEnabled(randomUserId())).toBeFalsy();
        }
    });

    it("should enable for more users if percentage grows", () => {
        let rolloutPercentage = 0;
        let previousBatch: string[] = [];
        const allUsers = new Array(1000).fill(0).map(() => randomDeviceId());

        while (rolloutPercentage <= 90) {
            rolloutPercentage += 10;
            const nextRollout = new PhasedRolloutFeature("test", rolloutPercentage);
            const nextBatch = allUsers.filter((userId) => nextRollout.isFeatureEnabled(userId));
            expect(previousBatch.length).toBeLessThan(nextBatch.length);
            expect(previousBatch.every((user) => nextBatch.includes(user))).toBeTruthy();
            previousBatch = nextBatch;
        }
    });

    it("should distribute differently depending on the feature name", () => {
        const allUsers = new Array(1000).fill(0).map(() => randomUserId());

        const featureARollout = new PhasedRolloutFeature("FeatureA", 50);
        const featureBRollout = new PhasedRolloutFeature("FeatureB", 50);

        const featureAUsers = allUsers.filter((userId) => featureARollout.isFeatureEnabled(userId));
        const featureBUsers = allUsers.filter((userId) => featureBRollout.isFeatureEnabled(userId));

        expect(featureAUsers).not.toEqual(featureBUsers);
    });
});
